Contamination Characterization and Mineralogical Investigation in an Arsenic and Heavy Metals Compound Contaminated Region to Elucidate Their Origin

초록

Soil contamination can be caused by various sources, such as natural, anthropogenic, and complex. The elucidation of such origins is a prerequisite for judging legal responsibility for remediation, establishing soil management plans, and other related matters. This study was conducted to reveal the origin of each contaminant in an arsenic and heavy metals compound contaminated region by the characterization of contamination according to soil depths, the investigation of chemical speciation using sequential extraction methods, the classification of contamination origin using principal component analysis (PCA), and the identification of arsenic-bearing minerals using mineralogical methods. The arsenic contamination levels of deep soils appeared to be similar to or relatively higher than those of top soils. In contrast, the contamination levels of cadmium and zinc in topsoils were significantly higher than those in deep soils. In addition, the results of sequential extraction analyses indicated that most of the arsenic existed in stable fractions with stronger binding strength, while cadmium and zinc were mainly fractionated into weakly bound and highly mobile species. The PCA results suggested that the origin of arsenic contamination was statistically significantly different from those of cadmium and zinc. Consequently, the arsenic contamination was likely to originate naturally, whereas cadmium and zinc were contaminated from anthropogenic sources. Finally, the results of mineralogical analyses to confirm the natural sources of arsenic contamination showed that it might be caused by the dissolution of arsenopyrite, which is widely distributed in the study area. This case study aimed to elucidate the origin of contamination using relatively simple conventional methods, and its findings are expected to be beneficial for related research.

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